A high-concept premise with a fiendishly claustrophobic setting, this film at least has the courage of its own convictions. And Reynolds delivers a relentlessly effective performance. So it's a shame that it's not more involving than it is.

After being ambushed while working as a driver in Iraq, private contractor Paul (Reynolds) wakes up in the dark, and his lighter shows him that he's inside a coffin-shaped wooden box. There's also a mobile phone in there, and soon Paul is communicating with the kidnapper (Perez), who demands that he make a video plea for ransom. Paul also contacts both his company's emergency manager (Tobolowsky) and a government agent (Paterson) who promises to help. But time is running out as Paul uses up both the breathable air and his phone battery.

Intriguingly, filmmaker Cortes avoids the temptation to cutaway to flashbacks, keeping us tightly contained in the box with Paul. The only other person we ever see is a colleague (Mino) who is also being held by the kidnappers and makes her own video. What's left are the range of voices on the other end of the line, plus Paul's continual movement as he tries to maintain a light source, avoid a visiting snake and stop the leaking sand.

The problem is that the script and direction continually betray the contrived set-up, as events feel rather pushy while dialog continually states the blatantly obvious: namely that Paul was woefully unaware of the dangers when he took the job. Of course these are valid points, but the script makes them without the use of irony or subtlety.

And then of course there's the problem of the gimmick itself. From the start, we get the feeling that, since we're so intimately trapped with Paul, there's no way the filmmakers will let him come to any harm. This essentially removes all tension; we feel his frustration, but never get a meaningful sense of his potential mortality. Perhaps this is due to Cortes' constantly moving camera, with clever angles that keep the film visually in motion. This is no small achievement for a film set in such a small space, but it gives away the biggest secret of them all: it's only a movie.